Impacting apparatuses (also referred to herein as a “driver,” “gun” or “device”) known in the art often may be configured for an entirely portable operation. Contractors commonly use power-assisted devices for impacting a surface and/or driving an object into a substrate. These power-assisted apparatuses can be portable (i.e., not connected or tethered to an air compressor or wall outlet) or non-portable.
A common impacting apparatus uses a source of compressed air to actuate a guide assembly to push an object into a substrate. For applications in which portability is not required, this is a very functional system and allows rapid delivery of fasteners for quick assembly. A disadvantage is that it does however require that the user purchase an air compressor and associated air-lines in order to use this system. A further disadvantage is the inconvenience of the device being tethered (through an air hose) to an air compressor.
To solve this problem, several types of portable impacting devices operate off of fuel cells. Typically, these guns have a guide assembly in which a fuel is introduced along with oxygen from the air. The subsequent mixture is ignited with the resulting expansion of gases pushing the guide assembly and thus driving an object into a substrate. This design is complicated and expensive. Both electricity and fuel are required as the spark source derives its energy typically from batteries. The chambering of an explosive mixture of fuel, the use of consumable fuel cartridges, the loud report and the release of combustion products are all disadvantages of this solution.
A final commercially available solution is to use a flywheel mechanism and clutch the flywheel to an anvil that impacts a substrate. This tool is capable of impacting very quickly. The primary drawback to such a tool is the large weight and size as compared to pneumatic counterparts. Additionally, the drive mechanism is very complicated, which gives a high retail cost.
Clearly, and based on the above efforts, a need exists to provide portable solution for impacting that is unencumbered by fuel cells or air hoses. Additionally, the solution ought to provide a low reactionary feel, and be simple, cost effective and robust in operation.
The prior art teaches several additional ways of impacting. The first technique is based on a multiple impact design. In this design, a motor or other power source is connected to an impact anvil through either a lost motion coupling or other device. This allows the power source to make multiple impacts on an object to drive it into a substrate. However, such multiple impact designs are not very efficient because of the constant motion reversal and the limited operator production speed.
A second design includes the use of potential energy storage mechanisms (in the form of a mechanical spring). In these designs, the spring is cocked (or activated) through an electric motor. Once the spring is sufficiently compressed, the energy is released from the spring into a striker, thus impacting the striker and/or a substrate. Several drawbacks exist to this design. These include the need for a complex system of compressing and controlling the spring, and in order to store sufficient energy, the spring must be very heavy and bulky. Additionally, the spring suffers from fatigue, which gives the tool a very short life. Finally, metal springs must move a significant amount of mass in order to decompress, and the result is that these low-speed impacting devices result in a high reactionary force on the user.
To improve upon this design, an air spring has been used to replace the mechanical spring, i.e., compressing air within a guide assembly and then releasing the compressed air by use of a gear drive. One particularly troublesome issue with this design is the safety hazard in the event that the anvil jams on the downward stroke and the operator tries to clear the jam, he is subject to the full force of the anvil, since the anvil is predisposed to the down position in all of these types of devices. A further disadvantage to the air spring results from the need to have the ratcheting mechanism as part of the anvil drive. This mechanism adds weight and causes significant problems in controlling the drive action since the weight must be stopped at the end of the stroke. This added mass slows the drive stroke and increases the reactionary force on the operator. Additionally, because significant kinetic energy is contained within the air spring and piston assembly the unit suffers from poor efficiency. This design is further subject to a complicated drive system for coupling and uncoupling the air spring and ratchet from the drive train, which increases the production cost and reduces the system reliability.
A third means for impacting that is taught includes the use of flywheels as energy storage means. The flywheels are used to launch a hammering anvil that impacts a substrate. One major drawback to this design is the problem of coupling the flywheel to the driving anvil. This prior art teaches the use of a friction clutching mechanism that is both complicated, heavy and subject to wear. Further limiting this approach is the difficulty in controlling the energy—the mechanism requires enough energy to impact effectively, but retains significant energy in the flywheel after the drive is complete. This further increases the design complexity and size of such prior art devices.
All of the currently available devices suffer from one or more the following disadvantages:                Complex, expensive and unreliable designs. Fuel powered mechanisms such as Paslode™ achieve portability but require consumable fuels and are expensive. Rotating flywheel designs such as Dewalt™ have complicated coupling or clutching mechanisms based on frictional means. This adds to their expense.        Poor ergonomics. The fuel powered mechanisms have loud combustion reports and combustion fumes. The multiple impact devices are fatiguing and are noisy.        Non-portability. Traditional impacting devices are tethered to a fixed compressor and thus must maintain a separate supply line.        High reaction force and short life. Mechanical spring driven mechanisms have high tool reaction forces because of their long drive times. Additionally, the springs are not rated for these types of duty cycles leading to premature failure.        Safety issues. The prior art “air spring” and heavy spring driven designs suffer from safety issues for impacting since the predisposition of the anvil is towards the substrate. During jam clearing, this can cause the anvil to strike the operator's hand.        The return mechanisms in most of these devices involve taking some of the drive energy. Either there is a bungee or spring return of the driving anvil assembly or there is a vacuum or air pressure spring formed during the movement of the anvil. All of these mechanisms take energy away from the drive stroke and decrease efficiency.        
In light of these various disadvantages, there exists the need for a fastener driving apparatus that overcomes these various disadvantages of the prior art, while still retaining the benefits of the prior art.